Tube-forming strip.



C. S. BIRD (in G. R. WYMAN.

TUBE FORMING STRIP. APPLICATION FILED 0 019, 1911.

1,101,990, Patented June 30,1914.

' fully "cnnntns s. BIRD I AND PA'rE ion TUBE-FORMING smrr.

Specification of Letters Patent. Patented June 30, 1914:. Applicationflledpcto'ber 9, 1911. Serial No. 653,641. a

formed.

One object of the invention is to so construct a tube forming strip thatno raw edges are present in the finished tube.

Another object of the invention is to so construct a tube forming striphaving a layer of insulating fiber or material of comparatively coarsequality that such layer, in the strip aswell as in the completed tube isprotected from contact or exposure.

Another object of the invention is. to so construct a tube forming stripthat, when said strip is formed into a tube, the drawing intosaid tubeof wires or other articles is facilitated.

Other objects of the invention will appear from the followingdescription.

The invention consists in a tube forming strip of material having itsedge portions turned inward whereby the edge of the strip is formed by afold of the material as distinguished from a raw cut edge of suchmaterial. p

The invention also consists in a tube forming strip comprising a fillingstrip and a layer of hard paper secured to said filling strip. g

The invention also consists in a tube forming strip comprising. afilling strip of comparatively coarse fibrous material and a Wrapper ofhard and comparatively fine paper secured to said filling strip andcovering the edges thereof.

The invention also consists in a tube forming strip having ridgesextending longitudinally or approximately longitudinally of the strip.

The invention also consists in such other novel features of constructionand combination of parts as shall hereinafter be more claimsp Figure 1,represents a plan view of the described and. pointed out in the improvedtube forming strip, in its preferred form, parts of the same beingbroken away to show the filling or insulating strip. Fig. 2, representsan enlarged sectional view of the strip as taken on line 22-Fig. 1, Fig.3, represents a. cross sectional view of a tube formed fro the improvedstrip as taken on line 33 4. Fig. 4, represents a view of a tube orconduit formed by bringing the edges of the strip together approximatelyin a straight line. Fig. 5, represents a view of a tube or conduitformed by winding-the improved strip spirally.

Similar numerals of reference designate corresponding parts throughout.

Strips of this nature are used to form the inner walls or surfaces oftubes and more particularly of tubes adapted to be used for insulatingconduits for electric wires which Wires are usually drawn into'the tubesafter the tubes are secured in building structures. Obviously it isimportant 'to so construct the tubes that the inner walls thereof] shallnot present raw edges whichv may retard the drawing in of the electricwires or cables by a tendency to engage the wrappings or insulatingcoverings of said wires or cables. It i is also of some importance that,where a strip of insulatin rfiber is incorporated in the wall of the tue, the raw edges of said strip be so confined thatthey cannot swell outor spring toward the bore of the tube.

In carrying our invention into practice in itspreferred form we take astrip'5 of coarse paper stock or of fibrous material constituting acore, and adapted, to some extent, to electrically insulate a wire orcable around which said strip is wrapped. This strip 5 is placed againstone surface of the outer stripl6 of hard strong paper and is preferablysecured thereto by adhesive, the edge portions of the strip 6 beingwrapped over, and preferably, secured. to the back of the strip 5whereby the edges, 7 7 of the complete stripare slightly rounded. Thecombined strips 5 and. 6 are now, or at some time during the process ofmanufacture passed through any suitable machine by which parallelcreases are formed in the wrapper 6 approximately longitudinally of thestrip whereby the ridges 8, 8 are formed by the material of wrapper 6 onthat surface thereof which is intended ultimately to form the innersurface or lining of the completed tube or conduit. When the strip isformed into a tube as shown in Figs. 4 'and5 for-insertion into a pipe,the

rounded longitudinal edges .7, 7 where they meet form a longitudinallyextending groove corresponding to those formedby the ridges v8, so thatthe're is no break in the continulty of the longitudinally rooved orcreased inner face of the insulating tube. The strip is reinforced andstrengthened by transversely extending ribs or creases 9 on the outerface thereof which are produced simultaneously with the forming of thecorrugated inner face, the formation of these ribs or creases leavingthe inner face of the strip indented transversely at spaced intervals asshown at 10, Fig. 1, where the forming die or roll compresses thematerial so as to force the same outwardly on the outer face and producethe ribbed or creasedouter face of the strip. We prefer that the strip 6be of suflicient width to wrap completely around the strip 5 as by thisconstruction the hard and closely condensed material of i i the strip orwrapper 6 to some extent protects the coarser fiber of strip 5 frommoisture.

It is not our intention to limit our invention by the above statement ofthe kind of material preferably used nor as to the shape or extensionofthe ridges or projections 8, 8' and it is obvious that such ridges orprojections may be omitted in some cases.

ping ends, the inner face 0 Having thus described our invention we claimas new and desire to secure by Letters Patent.

L A' strip adapted to form tubular insulation, comprising a core and arelatively length- 2.'A strip adapted to form tubular insu- I 1216011,comprising a core and a relatively thin covering therefor, the coveringbeing adhesively secured to the core and having a cross-sectionallengthto provide overlapping ends, the'inner face of the strip being creasedto provide a plurality of corrugations in the covering substantiallycontinuous in cross-section and extending length- Wise of the strip, thecreases extending into the core, said strip having lateral creasingsspaced apart and of greater width on the outer face than on the innerface.

' CHARLES S. BIRD.

,GEORGE E. WYMAN. Witnesses: I

H. H. MILLER, M. M. Burns.

